Cellular responses to exposure to ionizing radiation are determined by differential gene expression patterns. Signaling pathways regulate the cell cycle, repair processes and programmed cell death. The product of these biochemical events underlies radiation sensitivity or resistance. Our previous investigations have identified Raf-1, NF-kB and PARP as potential target molecules for cellular radiation sensitization strategies. We propose to advanced our investigations of antisense Raf-1 to a Phase II clinical trial in Project 6. NF-kB related targets will be verified in preclinical investigations using antisense to p65, or Ikk in Project 2. Novel mechanisms of PARP activity in transcriptional regulation, and in programmed cell death will be investigated to identify additional, potential, PARP-related targets in Projects 8 and 3. The EWS/Fli target for radiation sensitization of Ewing's sarcoma cells is the product of our previous investigations of PARP regulation. This molecule will be verified in preclinical studies for potential use in the treatment of Ewing's sarcoma in Project 4. Two cores are proposed: Core A to provide the needed administrative support and to foster scientific interactions among the program project members, and Core B to provide microarray analysis, atomic force microscopy, statistics, and radiation services; demanding technologies of common interest to investigators. The proposed projects build on our proven record of clinical translational research which centers on molecular mechanisms underlying cellular radiation responses. Data from these projects will identify and validate targets for use in clinical radiation sensitizing strategies to improve the therapeutic ratio for the treatment of human cancers.